Jet-engine silencer



Sept. 8, 1970 L. DUTHION ET AL 2 JET-ENGINE SILENCER Filed July 29, 1969 5 Sheets-Sheet 1 Filed July 29, 1969 Sept. 8, 1970 1.. DUTHION ETAL JET-ENGINE SILENCER 5 SheetsSheet 2 3 M I MA v L. DUTHION ETAL mw-znemm snnncsa Sept. s, 1910 5 Sheets-Sheet 5 filed my 29. 1969 Ft Q fl A u uuuuuuuuuuu uuuuuuu Sept. 8, 1970 DUTHION ETAL 3,527,318 Y JET-ENGINE SILENCER Filed July 29, 1969 5 Sheets-Sheet 4 Sept. 8, 1970 L. Dun-6N ET AL JET -ENGINE' SILENCER 5 Sheets-Sheet 5 Filed July 29, 1969' 7 M/MLZLL 161,35 Int. Cl. B64d 33/06; F01n 1/08, 1/14 U.S. Cl. 181-51 14 Claims ABSTRACT OF THE DISCLOSURE This invention relates to a jet-engine silencer, comprising essentially firstly a convergent element which is connected to the outlet pipe of the jet engine and branches into a plurality of parallel single convergent nozzles of elongate section through which the ejected gases issue in thin sheets mixing with secondary air drawn from the surroundings and, secondly, a ventilated divergent element which encloses the first element and whose upstream end is in the form of a frame provided with cores of elongate profile disposed at the exit of the respective convergent nozzles and forming single ventilated convergent-divergent nozzles.

This invention relates to a silencer, intended more particularly for jet engines, and, inter alia, supersonic aircraft power units, the outlet pipe of which has a substantially rectangular exit section.

The silencer according to the invention consists essentially of two basic elements, namely:

(a) An element having a convergent effect and hereinafter referred to as a convergent element, which is connected to the pipe and branches out into a plurality of parallel single convergent nozzles of elongate section, through which the gases ejected by the jet engine issue in thin sheets and mix with secondary air on the one hand and, if necessary, tertiary air on the other hand, such air being taken from the surroundings and admitted between the said nozzles. When the aircraft is stationary or on take-off, the secondary air is drawn in upstream of the convergent element by the nozzle exit gases, while when the aircraft is crusing the secondary air having a pressure greater than atmospheric pressure at the flight altitude mixes of its own accord with the nozzle exit gases.

Tertiary air is admitted to the convergent element only if a negative pressure forms in the secondary air passage, and this effect occurs more particularly when the aircraft is at a low speed.

(b) An element having a divergent effect and referred to as a ventilated divegent element which forms an extension of the first element and consists of a framework of streamlined cores forming a plurality of single ventilated convergent-divergent nozzles surrounding the exit end of each single convergent nozzle.

The dilution of the jet-engine ejection gases with the cold secondary air will therefore take place in this system of single two-dimensional ventilated convergent and convergent-divergent nozzles, which prevents any prohibitive fragmentation of the ejected gas jets and deceleration of the boundary layers, thus reducing losses due to friction and noise.

Preferably, guide blades are provided between the single convergent nozzles and, if necessary, between the boundary nozzles and the fairing of the ventilated divergent element, so that the secondary air may be directed towards the outlet section of the gases ejected from the said nozzles.

Preferably, the divergent element, and more particularly the cores, are of sound-absorbent materials.

3,527,318 Patented Sept. 8, 1970 Advantageously, the nozzles of the convergent element have at their downstream exit, movable flaps whose orientation can be adjusted to give nozzle exit sections adapted to the different speeds of the aircraft, In their end position, the gas outlet of each convergent nozzle can be closed, while reverse flaps are simultaneously opened to direct the ejected gas jet in the oposite direction to the direction of travel of the aircraft (so that a braking or reverse effect can be obtained). The flaps are disposed on the side walls of the single convergent nozzles and apertures are formed on the corresponding walls of the fairing of the divergent element.

This effect could be obtained by means of a device of known type disposed upstream of the convergent element, for example of the type described in the applicants French Pat. No. 1,481,950.

According to one embodiment of the invention, the convergent element is symmetrical with respect to a central longitudinal plane of the silencer and at its inlet it divides into two parts each comprising the single convergent nozzles whose outlet sections are substantially perpendicular to the central plane.

Similarly, the ventilated divergent element is symmetrical with respect to said plane and has a central core in said plane.

The single convergent nozzles may be bounded by flat walls, which are advantageously reinforced, and form a rectangular outlet section, but in order to reduce the weight of their structure while maintaining adequate strength they may alternatively be devised with orthogonally disposed corrugated walls. Another construction which also provides good strength, is to form the nozzles by using a plurality of tubes which may or may not be juxtaposed, so that the outlet section is inscribed in a substantially rectangular form.

Similarly, on the convergent element body, the movable flaps used to control the outlet section of the nozzles and the reverse flaps may be in appropriate forms, e.g., shields known per se in the form of half-shells.

The following description with reference to the accompanying drawings, which are given by way of example without limiting force, will clearly show how the invention may be performed, and the details disclosed in the drawings and the text naturally form part of the invention.

FIG. 1 is a diagrammatic perspective of a silencer according to the invention.

FIG. 2 illustrates two half-sections on the lines IIaIIa and IIb-IIb in FIG. 3, of the same embodiment of the invention.

FIG. 3 is a diagrammatic section on the line III-III in FIG. 2.

FIG. 4 is a partial section on the line IV-IV in FIG. 2, to an enlarged scale.

FIGS. 5 to 7 are diagrammatic details showing how the gas ejection flaps used for reverse are mounted and controlled.

FIG. 8 is a diagrammatic partial view in the direction A in FIG. 1 showing one surface of the ventilated divergent element comprising tertiary air passage traps and reverse jet passages.

FIG. 9 is a partial diagrammatic section on the line IX-IX in FIG. 8.

FIG. 10 is a partial view showing a second embodiment of the outlet section of the single convergent nozzles.

FIG. 11 is a partial view of a variant of FIG. 10.

In the exemplified embodiment shown in FIGS. l-3, the silencer comprises two main elements, namely a convergent element comprising single convergent nozzles 1, the inlet of which is provided, for example, with a cylindrical collar 2 so that it can be connected to the pipe 3 of a jet engine, and a divergent element 4 of substantially parallelepipedal shape which encases the convergent element and the downstream end of which bears a frame formed from corrugated cores 31, a central core 15 and peripheral cores 30.

According to FIG. 2, at the outlet of the collar 2, the convergent element divides into two symmetrical parts with respect to its central longitudinal plane P, each part comprising six single convergent elements 1 of elongate section in a plane substantially perpendicular to the plane P.

These noozles, one of which is shown in section in half of FIG. 2, while they are shown in side elevation in the other half, are progressively connected to the collar 2 and between them they form longitudinal passages 6 (FIG. 3), the downstream ends of which are formed by single ventilated convergent-divergent nozzles 32 bounded by the corrugated cores 31.

The passages 6 serve for the introduction of secondary air and the mixing thereof with the ejected gases takes place at the inlet of the single ventilated convergentdivergent nozzles 32 and undergoes expansion in the divergent element of said nozzles. The passages 6 have guide blades 7 to promote the flow of secondary air.

Such blades may also be provided between the walls of the boundery nozzles and the side walls of the divergent element.

As will be seen in FIG. 3, the downstream sections of the single convergent nozzles may be closed by movable flaps 8 pivotally connected to pivots 9 perpendicular to the plane P.

These flaps are controlled in pairs by jacks or actuators 10 pivotally connected to the divergent element 4 and linkages 11 so that they can be oriented either in parallel relationship to the pulsating jet as shown in half of FIG. 2, which is the normal operating position in which the aircraft is stationary, or be brought together into a closure position as shown by the other half of the figure, which is the reverse position, or intermediate positions corresponding to operation of the aircraft at different cruising speeds.

The reverse flaps are controlled as follows referring to FIG .2: each linkage 11 is pivotally connected at one end of a rocker 12 which pivots about a stationary pivot 13 rigidly secured to a support 14 fixed to the central core 15 of the divergent element. The other end of the rocker controls a rod 16 by means of a fork 42 which by means of the two pivots 41 is pivotally connected to the rocker 12 while it is pivotally connected to the rod 16 by the pivot 43 as shown in FIG. 4. At various places the rod 16 has pivots 17 to which links 18 are symmetrically pivotally connected and terminate in swivel joints 19 engaging in corresponding housings 20 with which the flaps 8 are provided. The rods 16 are disposed in register with the secondary air passages so that when the said rods are moved in the direction of arrow F in FIG. 4- the flaps 8 are pushed towards the central plane of the nozzles so that the latter are closed.

Racks (FIG. 2) are secured, e.g. welded, to the end of the rods 16 and mesh with pinions 28 so that two rods or bars 16 disposed symmetrically with respect to the plane P are coupled.

The pinions 28 of each pair of rods or bars are also mounted, e.g. keyed on the same pinion shaft 29 in order to synchronise opening and closing of the reverse flaps and thus obviate any failure of one of the closure systems of the said flaps.

When the convergent nozzles are closed by the flaps 8, the ejected gas jet is delivered towards the upstream end of the convergent element and means are used to ensure their evacuation. For this purpose, as shown in FIGS. 5- 7, the outer side wall of each of the nozzles 8 is open and provided with reverse flaps 21 whose elements are pivoted about transverse pivots 22 extending parallel to the central plane of the silencer. As shown in FIG. 5, these elements are so disposed that when they are folded down along the wall of the nozzle they close the latter without oifering any resistance to the gas flow.

They may be open by an angle of about 60 in the forward direction by means of a linkage comprising cranks 23 keyed on pivots 22. These cranks, which are identical and parallel to one another are pivotally connected on a link 24 which allows them all to be moved together. The link 24 has a side lug 25 (FIGS. 6 and 7) which engages in a S-shaped slot 26 in a plate 27 rigidly secured to the corresponding linkage 11. In this way the control of the reverse flaps is synchronised with the control of the flaps 8. However, when the lug 25 is in the straight part of the S, the flaps 8 can close a certain angle while the reverse flaps are still closed, and this is advantageous for controlling the outlet sections of the single convergent nozzles to adapt them to different flight conditions. Only when the lug 25 is on the curve of the S are the flaps 8 I closed with the simultaneous opening of the reverse flaps In register with the reverse flaps 21, apertures 33 are formed in the wall of the divergent element 4 (FIGS. 8 and 9) to allow the gas jet to escape to the surroundings and produce the reversing effect. Calibrated traps 34 are formed between each aperture 33 to admit tertiary air when a negative pressure occurs in the secondary air passage. The traps 34 open in the direction of the arrows shown in FIG. 9.

As will be apparent from FIG. 1, the divergent element 4 is closed by a thin casing of rectangular section. It comprises two walls 35 stiffened by U-cross-members. These walls are advantageously lined with sound-absorbent material, e.g. glass wool. The peripheral cores forming the continuation of these walls are streamlined. Corrugated cores 31 are provided in parallel relationship to the nozzles 1 and their upstream ends engage in the passages 6 separating the convergent nozzles. The cores 31 enclose the supports 14 and the rods or bars 16 and the control system for the movable flaps 8. They are also lined with sound-absorbent material.

In the central plane of the silencer, the corrugated cores 31 are stiffened by the central core 15 already mentioned in the description of the system for controlling the flaps 8.

In the first embodiment shown in FIGS. 1, 2 and 3, the single convergent nozzles consist of flat walls 36 advantageously reinforced by ribs 37 forming a rectangular outlet section (FIG. 1).

In a second embodiment shown in FIG. 10, the single convergent nozzles are formed by corrugated walls 38 forming a substantially rectangular section.

Finally, in a third embodiment shown in FIG. 11, the single convergent nozzles are formed by a plurality of tubes 39 connected by walls 40, and the outlet section is inscribed in a substantially rectangular form.

Of course, modification may be made to the above described embodiments, more particularly by the substitution of equivalent technical means, without thereby departing from the scope of the invention.

We claim:

1. A jet-engine silencer, comprising essentially firstly a convergent element which is connected to the outlet pipe of the jet engine and branches into a plurality of parallel single convergent nozzles of elongate section through which the ejected gases issue in thin sheets mixing with secondary air drawn from the surroundings and, secondly, a ventilated divergent element which encloses the first element and whose upstream end is in the form of a frame provided with cores of elongate profile disposed at the exit of the respective convergent nozzles and forming single ventilated convergent-divergent nozzles.

2. The silencer set forth in claim 1, wherein guide blades are disposed in passages formed between said nozzles.

3. The silencer set forth in claim 1, wherein said ventilated divergent element is constructed from sound-absorbent materials.

4. The silencer set forth in claim 1, wherein in register with outlet orifices of said single convergent nozzles are movable flaps which can be brought together in pairs in order to adjust the outlet section of said nozzles or close them.

5. The silencer set forth in claim 4, wherein side walls of said nozzles are provided with reverse flaps.

6. The silencer set forth in claim '5, wherein, as from a certain angle of closure of said movable flaps, a synchronisation system is operable to simultaneously open said reverse flaps and vice-versa.

7. The silencer set forth in claim 6, wherein said synchronisation system is in the form of jacks or actuators which control said movable flaps by means of rockers and push-rods and said reverse flaps by means of slide-guides.

8. The silencer set forth in claim 6, wherein said synchronisation system for controlling said movable flaps and said reverse flaps is mounted on said divergent element.

9. The silencer set forth in claim 1, wherein said convergent element is symmetrical with respect to the central longitudinal plane of the silencer and divides into two parts situated on either side of said plane.

10. The silencer set forth in claim 9, wherein said ventilated divergent element has a central profiled core in said central longitudinal plane of the silencer. v

11. The silencer set forth in claim 1, wherein said single convergent nozzles have a rectangular outlet section bounded by flat walls containing stiffening means,

12. The silencer set forth in claim 1, wherein said single convergent nozzles have a rectangular outlet section bounded by corrugated walls.

13. The silencer set forth in claim 1, wherein said single convergent nozzles are formed by a plurality of tubes whose outlet sections are inscribed in a rectangle.

14. The silencer set forth in claim 1, wherein side walls of said ventilated divergent element have exhaust apertures for reversing gases and traps for the admission of tertiary air.

References Cited UNITED STATES PATENTS 2,886,946 5/1959 Parker. 3,027,713 4/ 1962 Tyler et al. 3,143,184- 8/ 1964 Denning et al. 3,333,772 8/ 1967 Bruner.

FOREIGN PATENTS 609,979 12/ 1960 Canada. 844,179 8/ 1960 Great Britain.

ROBERT S. WARD, 111., Primary Examiner US. Cl. X;R. 

